I followed the links, macc, lol. What's the problem again?

Although I don't use a helmet light right now, the one I have used up until summertime was a simple Energizer 6-LED headlamp. They're cheap, bright (much better than my actual bike headlamp), long-lasting and strap on nicely. The strap is adjustable and the back of the light has a nice piece of grippy foam rubber so it can't slide around on your helmet, but long-term, I can see the strap eventually fraying/wearing out. The best part is that the light will tilt down into three or four positions so that you can focus into the roadway instead of just straight ahead.

I had it zip-tied to my backpack for a few days to make use of the light's two red LEDs (minimal visibility; better than nothing), but I'll eventually design a clip mount for my helmet so I can get rid of the strap altogether.